A rational number is any integer, fraction, terminating decimal, or repeating decimal.
1.) 101 is a rational number
2.) 8/17 (can't tell what it is) all fractions are rationales though, so doesn't matter
3.) 21.792 is rational (can't tell if its a 1 or seven, but both would be rational)
4.) √ 7 is not rational
5.) √9 is rational
6.) pi is never rational
7.) √50 is not rational
8.) 39.81... is rational